Materials separation apparatus and method of materials separation



H. M. CHAPMAN MATERIALS SEPARATION APPARATUS AND METHOD OF MATERIALSSEPARATION Flled July 20 1956 July 28, 1959 INVENTOR CHAZMAN HAQRLOW MUnited States PatrhtDfiFice 2,896,744 Patented July' 28, 1959 MATERIALSSEPARATION APPARATUS AND METHOD OF MATERIALS SEPARATION Harlow M.Chapman, Bethlehem, Pa.

Application July'ZO, 1956, Serial No. 599,197

4 Claims. (Cl. '18383) This invention relates to apparatus forseparating particles of different densities and is especially directedto a novel and improved collector primarily for separating and removingdust particles and the like from a stream of moving air or gas althoughlike principles of operation may be utilized for effecting otherseparations if desired.

Numerous dust collectors have heretofore been proposed dependent fortheir operation upon centrifugal force and thus so constructed as toimpart to a moving stream of dust-laden air or gas a rotary or spiralmotion converting a rectilinear velocity into a centrifugal force whichtends to cause the particles to congregate together in the radiallyoutermost layer of the stream and thus deprive the innermost layers ofmost of their burden thereof so that after the air has traversed anumber of convolutions of a spiral or helical path it is dischargedaxially of the confining chamber relatively free of contaminatingparticles, the latter, usually more or less coalesced into a relativelydense mass, falling to the bottom of the chamber for passage to asuitable receptacle Or for other disposition.

I have found that for dust collectors of this type to be effective theymust be so proportioned that the spiral air stream initially winds itsway downward for a number of revolutions and then upward on a smallerradius and in the same direction of rotation, thus producing a spiral ofopposite lead, that is, when the outer spiral corresponds generally to aright hand thread the inner one corresponds to a left hand thread andvice versa. As a result there is a zone between the two inwardly ofwhich the air is moving in a direction in conflict with the direction ofthe immediately adjacent air in the outer zone, creating an intermediatezone of counterflow friction in which the average linear velocity ofparticles of air, and dust, is less than the average of the velocitiesof the immediately inward and outward particles in the other zones.Since to escape radially from the inner zone any particle still carriedby the air must pass through the said intermediate zone of lower linearVelocity, it is apparent that any increased linear velocity in the innerzone derived from decreased radius of the spiral path, which mightnormally be expected to improve effectiveness in separating out anyremaining particles, is largely counteracted by the slow moving air inthe intermediate zone.

Furthermore, due primarily, it is believed, to the said counter flowfriction at the intermediate zone interfaces power requirements ofcollectors of the type just described are excessive considering theirrelatively low elficiency.

' It is' therefore an object of the invention to provide separatingapparatus such as a dust collector in which, while centrifugal force isrelied upon to carry outwardly the denser particles in a moving streamcontaining particles of different densities when the path of movement ofthe stream is curved about an axis, a relatively thin vlayer of thelighter particles, that is, dust free air or gas, is separated from theremainder of the stream before completing even one complete revolutionabout the collector axis, and on each succeeding revolution of the mainstream a further inner and hence dust free layer is similarly separatedtherefrom until after traversing several spiral convolutions of the pathvirtually all dust particles have been forced to the outer limits of theconfining chamber and carried or allowed to fall into a subjacent hopperor other receiver and the dust free air or gas separated from them hasbeen discharged from the collector separating chamber.

A further object is to provide a method of separating dense particlesfrom lighter ones in a moving stream of air or gas containing a mixturethereof by diverting the stream into an arcuate path and then aftercentrifugal force has removed the denser particles from the radiallyinnermost portion of the stream separating said portion from the latterand thereafter during successive revolutions of the denser particles andthe remaining lighter ones about an axis in a spiral or helical pathsimilarly separating portions of the stream centrifugally freed ofdenser particles until substantially all the latter originally containedin the stream have been collected in a receptacle and a stream of lessdense material substantially freed therefrom remains for discharge fromthe collector.

Other objects, purposes and advantages of the invention will hereaftermore fully appear or will be understood from the following descriptionof a preferred embodiment of it specifically adapted for service as adust collector for separating dust from air or gas and illustrated inthe accompanying drawing in which:

Fig. l is a side elevation of the collector partly broken away insection to show internal construction;-

Fig. 2 is a section on line 2-2 in Fig. 1; and

Fig. 3 is a section on line 33 in Fig. l, the latter two figures beingtaken looking respectively in the directions of the arrows on thesection lines.

Referring now more particularly to the drawing, the dust collectortherein illustrated comprises a main housing 1 defining a substantiallycylindrical chamber having a flat cover plate 2 at its top through whichan axial exhaust duct 3 extends for conducting the dust-free air fromthe cleaner. At its lower end the housing is in the form of an invertedfrustum of a cone forming a dust collecting hopper 4 discharging into anaxial discharge pipe 5, and an inlet duct 6 substantially tangential tothe housing near its upper end and discharging thereinto provides apassage through which dust laden air is admitted into the housingchamber, duct 6 being preferably rectangular in cross sectionparticularly at its inner end Where it is connected with the housing. i

The elements of the dust collector thus far described are notsubstantially different from corresponding elements in dust collectorsheretofore well known in the art and detailed discussion of their form,construction and assembly therefore would be superfluous. Internally ofthe housing, however, this does not apply, since in prior dustcollectors of this general character an axial exhaust duct,corresponding to duct 3, usually extends in the housing considerablybeyond the transverse plane of the lower edge of the inlet duct. Inaccordance with the invention, however, duct 3 as a cylindrical ductterminates approximately in alignment with the transverse plane of thebottom face 7 of duct 6 and is provided with a downwardly projectingbafile 8 extending from its lower end in the housing chamber in adiverging semispiral whereby, while the baffle is generally in the formof a slotted frustum of a hollow cone, a narrow inverted V-shaped slot 9lying substantially in a radial plane from the housing axis is formed,being positioned to intercept progressive increments of air introducedto the housing through duct 6 after traversing either a little less thanone full circuit about the housing axis or that distanoe plus a wholenumber of additional full circuits thereabout in a counterclockwisedirection in Fig. 2. To attain this result the plane of the opening ofslot 9 may coincide with the plane of that diameter of the chamber,designated C in Fig. 3, which parallels the direction in whichthe airtravels in the tangential inlet duct 6 just prior to its introductioninto the housing, which direction may be deemed as being represented onthe average as substantially coincident withthe center plane D of theduct; the plane of the slot opening may be more remote than the plane Cfrom the plane D but it is inadvisable to position it appreciably closerthan plane C to plane D as contamination of dust free air by dust ladenair entering through duct 6 may result if the relationship described isnot substantially observed. Slot 9 iin the baffle diverges toward thebottom of the housing and is thus Widest at the lower edge 10 of thebaffle, this edge of the batfie conforming substantially to an are drawnabout the housing axis for about a semicircle from the radiallyoutermost lower corner 11 of slot 9 and there converges inwardly in aspiral segment to the innermost lower corner 12 of slot 9, the edge 10providing throughout its length a clearance 13 from the housing wall ofat least sufficient width to permit the largest particles andaccumulations of dust collected in the superjacent portion of thecollector to fall into the hopper below, the preferred conformation ofthe baffle edge being apparent from Fig. 3.

In operation this collector is supported in upright position with duct 6connected to a source of dust laden air or the like and the exhaust duct3 to a chamber (not IT 1 shown) into which dust-free'air is to bedischarged, or if preferred left open to the atmosphere, while the dustdischarge pipe 5 is preferably connected to a suitable receptacle (notshown) for the collected dust.

As the dust laden air is introduced to housing 1 through duct fiatrelatively high linear speed, preferably of the order of 1500 or moreper minute, the tangential arrangement of the duct with relationship tothe housing causes the latter to divert the air stream and guide it intoan arcuate path about the housing axis. On this diversion of therelatively low density air the inertia of the higher density dustparticles causes them to congregate by centrifugal force toward theradially outward portions of the stream, and a thin radially innermostlayer of the stream is almost immediately freed of dust so that by thetime'the air particles in this layer have completed slightly less thanone full circuit or revolution in the housing and attained the uppernarrower end of slot 9 they are in condition for discharge into exhaustduct 3. The remaining air in the stream, containing all the dust in theoriginal stream, is forced by the dust laden air following it tocontinue in its circular, or by now spiral or helical course about thehousing axis for further successive revolutions at the end of each ofwhich another inner layer has been freed of dust and is discharged orpeeled off from the stream when slot 9 is progressively reached.

The downward divergence of bafile 8 affords a gradually decreasing crosssectional area for passage of the stream, preferably correspondinggenerally to the diminution of its volume resulting from discharge ofits inner layer at slot 9 on each spiral revolution whereby linearvelocity is maintained, or even perhaps slightly increased, insuringthorough cleaning of the air, so that when the dust-free air particlesare reunited in a single stream in exhaust duct 3 there is relativelylittle turbulence in the stream which therefore passes out through duct3 with minimum expenditure of power.

Moreover, it will be noted the spiral movement of the stream downwardlyin the housing is not obstructed or retarded by counter flow frictionagainst an inner upwardly spiraling stream, bafiie 8 separating airmoving in these conflicting directions from each other, while inpractice it may be shown that but a small proportion, if any, of the airintroduced through duct 6 ever moves into duct 3 after passing aroundthe lower edge 10 of the baflle, the stream of air spiraling about theaxis as it approaches this edge being repeatedly attenuated on eachconvolution of the spiral as it passes slot 9 so but little, if any,rapidly moving air normally reaches the lower corners 11, 12 of the slotand that below edge 10 of the baffle is relatively still, being movedonly by particles of dust falling through it, and such particles thusaccumulate in the hopper portion of the collector and fall therefromthrough discharge pipe 5 by gravity and with little or no chance oftheir recirculation into the superja'cent moving air stream.

By thus eliminating counter flow friction between adjacent movingstreams of more or less dust laden air my collector avoids wastefulexpenditure of energy in counteracting such friction and by deliveringto the exhaust duct progressive increments of air substantiallyimmediately after separation of the dust therefrom the energy otherwiserequired to force all air introduced into the cleaner to follow the sameelongated path afiords further material savings in energy with theresult that a collector of any given size constructed in accordance withthe invention cleans with equal or better efficiency a substantiallylarger quantity of air per unit of time than others of comparable size,or as much as other collectors materially larger in size, and withmaterially less expenditure of power.

While I have herein described with considerable par ticularity oneembodiment of the invention which has been found highly efficient andeconomical in power requirements and hence Well adapted for use as adust collector in freeing air or gas of mineral dusts and the like, itwill be understood the principles utilized in its construction andoperation may have application in effecting separations of differentcharacter, and consequently that 'I do not desire hereby to precludetheir use for such purposes or otherwise to limit or confine theinvention in any way, and further, that such changes and modificationsin the form, structure, mode of assembly, arrangement and relationshipof the several components of the collector as may occur to those skilledin the art may be made if desired without departing from the spirit andscope of the invention as defined in the appended claims.

Having thus described my invention, I claim and desire to protect byLetters Patent of the United States:

1. In a collector or the like, the combination with means forming asubstantially cylindrical separating chamber, means for introducingtangentially thereinto a stream of fluid containing finely dividedparticles of greater density than the fluid, and means providing anaxial exhaust passage from the chamber, of a baffle extending in thechamber from the lower end of said last mentioned means angularlyoutwardly and downwardly and providing a slot communicating with saidexhaust passage lying substantially in a radial plane from. the chamberaxis spaced from the plane of said introducing means at least as far asthe plane of that diameter of the'chaniber which parallels saidintroducing means having side edges diverging outwardly and downwardlyin said radial plane.

2. A collector as defined in claim 1 in which said radial plane liessubstantially parallel to the tangential path of the fluid streamintroduced into the chamber.

3. In a collector or the like, the combination with means forming asubstantially cylindrical separating chamber, means for introducingtangentially thereinto a stream of fluid containing finely dividedparticles of greater densitythan the'fiuid, and means providing an axialexhaust passage from the chamber, of a baffie extending in the chamberfromthe lower 'end of said last mentioned means angularly outward anddownward and providing a slot communicating with said exhaust passageandlying substantially in a radial plane from the chamber axis, saidslot having side edges diverging outward and downward in said plane,every transverse section of the baflle comprising an approximatelysemi-circular segment extending from one edge of the slot and a spiralsegment extending therefrom to the other edge of the slot, the radii ofsaid segments increasing in length as the sections are progressivelytaken downwardly from the upper end of the baffle.

4. In a collector or the like, the combination with means forming asubstantially cylindrical separating chamlber, means for introducingtangentially thereinto a stream of fiuid containing finely dividedparticles of greater density than the fluid, and means providing anaxial exhaust passage from the chamber, of a bafile extending in thechamber from the lower end of said last mentioned means angularlyoutward and downward and providing a slot communicating with saidexhaust passage lying substantially in a radial plane from the chamberaxis having side edges diverging outward and downward in said plane, thebafile at its lower edge being substantially uniformly spaced from theadjacent inner wall of the separating chamber for approximately 180 fromone end of said edge and thence substantially conforming to acontracting spiral to the other end of said edge.

References Cited in the file of this patent UNITED STATES PATENTS678,451 Allington July 16, 1901 969,769 Brassert et a1. Sept. 13, 19101,444,585 Collins Feb. 6, 1923 2,349,831 Osgood May 30, 1944 2,719,631Vicard Oct. 4, 1955 FOREIGN PATENTS 273,475 Great Britain July 7, 19 27

